Figure 1

Study threshold determination and block procedure. (A) Determination of threshold in behavioral session. 1 Participants read a Footbridge-type dilemma in the behavioral session. Red: The participant in the scenario; White: the people that they would kill in the scenario; Blue: the people that would be saved in the scenario because they killed the others. 2 Participants were presented with 10 repetitions of each stimulus in a randomized order. 3 Based on the percentage of YES and NO responses for each stimulus in the preceding session, the threshold (dashed red vertical line) was calculated. 4 Finally, the stimuli immediately below and above the threshold - the Individualized stimuli - as well as two other stimuli Shared by all participants - 1:11 and 10:2 - were the only stimuli presented to participants in the subsequent EEG session. (B) Block procedure for the behavioral and EEG session. The participant was presented one of three Footbridge-type dilemmas, which they read at their own pace. The trials were preceded by a fixation cross for a jittered duration of either 5, 5.5 or 6 seconds (randomized). The stimuli were a black screen with white two-dimensional stick people on either side of the screen, with a white line and fixation cross down the middle. The instructions given were that the people on the left side were those that would be killed in the previously read scenario, while the people on the right were those that were saved because of the others dying. Participants were instructed to respond either YES or NO if the numbers of killed to saved presented in the stimulus were acceptable to them. The maximum duration of the stimulus was 2 seconds. In the EEG session, each block was comprised of 60 trials, with each stimulus being presented 15 times. ITI = intertrial interval.